全文获取类型
收费全文 | 681篇 |
免费 | 35篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 133篇 |
金属工艺 | 36篇 |
机械仪表 | 23篇 |
建筑科学 | 2篇 |
能源动力 | 21篇 |
轻工业 | 5篇 |
石油天然气 | 9篇 |
无线电 | 89篇 |
一般工业技术 | 241篇 |
冶金工业 | 33篇 |
原子能技术 | 18篇 |
自动化技术 | 104篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 20篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 38篇 |
2013年 | 55篇 |
2012年 | 49篇 |
2011年 | 76篇 |
2010年 | 56篇 |
2009年 | 51篇 |
2008年 | 49篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 21篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 13篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有719条查询结果,搜索用时 15 毫秒
41.
Dmitri Moltchanov 《Computer Science Review》2010,4(3):153-184
Performance modeling of wireless access technologies is useful to understand their limitations in various operational conditions and find a way to improve their performance. In the past two decades a number of models have been proposed. These models are often more complicated compared to those developed for wired networks. The reason is that in wireless networks performance degradation is caused by both incorrect reception of channel symbols at the physical layer and queuing at higher layers. Various error control mechanisms used to hide the effect of error-prone channel behavior complicate performance analysis and often require restrictive assumptions to retain analytical tractability. The aim of this paper is to review performance evaluation models proposed for wireless channels, highlighting their basic ideas, shortcomings, and advantages. We consider models developed for both centralized and distributed access technologies. Potential applications and extensions are also discussed. We believe that this study may provide a starting point for those looking for a suitable modeling framework and allow time to be saved in developing new performance models. 相似文献
42.
43.
B. D. Rogozkin N. M. Stepennova Yu. E. Fedorov M. G. Shishkov F. N. Kryukov S. V. Kuzmin O. N. Nikitin A. V. Belyaeva L. M. Zabudko 《Atomic Energy》2011,110(6):412-429
The results of post-reactor studies of U0.55Pu0.45N and U0.4Pu0.6N mixed mononitride fuel elements (density 85% of the theoretical value) and a helium sublayer are presented. The fuel elements
are irradiated in a BOR-60 reactor to burnup 9.4 and 12.1% h.a., respectively, with power density 430 and 540 W/cm. All fuel
elements remained hermetic; the ChS-68 steel cladding (20% cold deformation) retained excess plasticity. The maximum zone
of interaction between the cladding and the fuel and fission products did not exceed 15 μm. The swelling rate of U0.4Pu0.6N and U0.55Pu0.45N fuel was 1.1 and 0.68%/% burnup, respectively. The gas release did not exceed 19.3 and 19%. The steel damage dose was 43
dpa. The character of the porosity distribution in the fuel affects the swelling and gas release. 相似文献
44.
A direct numerical inversion method for the determination of the refractive index and the thickness of the outermost layer of a thin transparent film on top of a multilayer has been developed. This method is based on a second-order Taylor decomposition of the coefficients of the Abelès matrices of the newly grown layer. The variations of the real-time spectroscopic ellipsometry data are expressed as polynomial fuctions depending on the dielectric constant and the thickness of the newly grown layer. The method is fast, capable of single-wavelength and multiwavelength inversion of continuous as well as discontinuous-index profiles, and can be adapted to many different polarimetric instruments. 相似文献
45.
Pattern storage and processing in attractor networks with short-time synaptic dynamics 总被引:3,自引:0,他引:3
Neurophysiological experiments show that the strength of synaptic connections can undergo substantial changes on a short time scale. These changes depend on the history of the presynaptic input. Using mean-field techniques, we study how short-time dynamics of synaptic connections influence the performance of attractor neural networks in terms of their memory capacity and capability to process external signals. For binary discrete-time as well as for firing rate continuous-time neural networks, the fixed points of the network dynamics are shown to be unaffected by synaptic dynamics. However, the stability of patterns changes considerably. Synaptic depression turns out to reduce the storage capacity. On the other hand, synaptic depression is shown to be advantageous for processing of pattern sequences. The analytical results on stability, size of the basins of attraction and on the switching between patterns are complemented by numerical simulations. 相似文献
46.
A vector (multicriterion) problem of integer linear programming is considered on a finite set of feasible solutions. A metric
lp, 1 ≤ p ≤ ∞, is defined on the parameter space of the problem. A formula of the maximum permissible level of perturbations
is obtained for the parameters that preserve the efficiency (Pareto optimality) of a given solution. Necessary and sufficient
conditions of two types of stability of the problem are obtained as corollaries.
This work has been carried out with financial support from the Belgosuniversity within the framework of the Intercollegiate
Program “Fundamental and Applied Investigations” (project No. 492/28).
__________
Translated from Kibernetika I Sistemnyi Analiz, No. 4, pp. 175–181, July–August 2006. 相似文献
47.
Su Z Vinogradova A Koutychenko A Tolkatchev D Ni F 《Protein engineering, design & selection : PEDS》2004,17(8):647-657
The tetrapeptide Phe-Asn-Pro-Arg is a structurally optimized sequence for binding to the active site of thrombin. By conjugating this tetrapeptide or some variants to a C-terminal fragment of hirudin, we were able to generate a series of new bivalent inhibitors of thrombin containing only genetically encodable natural amino acids. We found that synergistic binding to both the active site and an exosite of thrombin can be enhanced through substitutions of amino acid residues at the P3 and P3' sites of the active-site directed sequence, Phe(P4)-Xaa(P3)-Pro(P2)-Arg(P1)-Pro(P1')-Gln(P2')-Yaa(P3'). Complementary to rational design, a phage library was constructed to explore further the residue requirements at the P4, P3 and P3' sites for bivalent and optimized two-site binding. Very significantly, panning of the phage library has led to thrombin-inhibitory peptides possessing strong anti-clotting activities in the low nanomolar range and yet interfering only partially the catalytic active site of thrombin. Modes of action of the newly discovered bivalent inhibitors are rationalized in light of the allosteric properties of thrombin, especially the interplay between the proteolytic action and regulatory binding occurring at thrombin surfaces remote from the catalytic active site. 相似文献
48.
Ma R Golberg D Bando Y Sasaki T 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2004,362(1823):2161-2186
The current status of research on boron-carbon-nitrogen (B-C-N) and boron nitride (BN) nanotubes is presented. The latest achievements in syntheses, analyses and property measurements of these nanoscale tubular architectures are reviewed. The characteristic features of B-C-N and BN nanotubes, compared with conventional C nanotubes, are paid special attention. In particular, the latest breakthroughs in the chemical vapour deposition synthesis of BN nanotubes and an insight into their unique structures are highlighted. A wide range of potential applications is also envisaged, based on the recent progress, which includes pioneering results in BN nanocable fabrication, gas adsorption, electron transport and field emission measurements. 相似文献
49.
The efficient processing of multidimensional similarity joins is important for a large class of applications. The dimensionality of the data for these applications ranges from low to high. Most existing methods have focused on the execution of high-dimensional joins over large amounts of disk-based data. The increasing sizes of main memory available on current computers, and the need for efficient processing of spatial joins suggest that spatial joins for a large class of problems can be processed in main memory. In this paper, we develop two new in-memory spatial join algorithms, the Grid-join and EGO*-join, and study their performance. Through evaluation, we explore the domain of applicability of each approach and provide recommendations for the choice of a join algorithm depending upon the dimensionality of the data as well as the expected selectivity of the join. We show that the two new proposed join techniques substantially outperform the state-of-the-art join algorithm, the EGO-join. 相似文献
50.
Yeonjong Koo Ekaterina Y. Lukianova‐Hleb Joann Pan Sean M. Thompson Dmitri O. Lapotko Janet Braam 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(5):623-630
Biological responses to photothermal effects of gold nanoparticles (GNPs) have been demonstrated and employed for various applications in diverse systems except for one important class – plants. Here, the uptake of GNPs through Arabidopsis thaliana roots and translocation to leaves are reported. Successful plasmonic nanobubble generation and acoustic signal detection in planta is demonstrated. Furthermore, Arabidopsis leaves harboring GNPs and exposed to continuous laser or noncoherent light show elevated temperatures across the leaf surface and induced expression of heat‐shock regulated genes. Overall, these results demonstrate that Arabidopsis can readily take up GNPs through the roots and translocate the particles to leaf tissues. Once within leaves, GNPs can act as photothermal agents for on‐demand remote activation of localized biological processes in plants. 相似文献